The architecture of present day mobile network includes a radio access network, a core network and user equipment connecting to the radio access network. The radio access network includes radio base stations or nodes for setting up the connection to the user equipment.
Whilst the nodes of the radio access network mainly can be considered as stationary with fixed location, the user equipment is mobile and may take basically any position within the network. Planning, configuring, optimizing, and maintaining a radio access network, the mobile operator must ensure a radio propagation behavior in the system that corresponds to the location of user equipment in the network. Today, operators resort to planning tools to dimension and plan their networks according to a specific business strategy. The approach based on planning tools and prediction is, however, not fully accurate. Reasons for the inaccuracies are imperfections in the used geographic data, simplifications and approximations in the applied propagation models, and changes in the environment, e.g., construction/demolition or seasonal effects (foliage changes). Furthermore, changes in the traffic distribution and user profiles can lead to inaccurate prediction results. The above mentioned shortcomings force operators to continuously optimize their networks using measurements and statistics, and to perform drive/walk tests. Drive/walk testing provides a picture of the end user perception in the field and enables the operator to identify locations causing poor performance and their corresponding cause (e.g., incorrect tilt or handover settings). Drive/walk tests are, however, not ideal since only a limited part of the network can be analyzed due to access restrictions and the cost and time involved. Further, only a snapshot in time of the conditions in the field is captured. Wireless network operators today have considerable manual effort in network management, e.g., configuring the radio access network. These manual efforts are costly and consume a great part of operational expenditures (OPEX).
e-UTRAN (evolved UMTS Terrestrial Radio Access Network) is a future wireless access network standard optimized for packet data and providing higher data rates. An important E-UTRAN requirement from the operators' side is a significant reduction of the manual effort in network management for this future wireless access system. This involves automation of the tasks typically involved in operating a network, e.g., planning, verification through, e.g., drive/walk testing, and optimization.
A method for improving network management in e-UTRAN is to use the user equipment (UE) reports. The UE can report anything that can be configured via the radio resource control measurement control and reporting procedures. A standardization of such UE reports is carried out within 3GPP. The user equipment collects data to determine observed service quality, e.g., RF signal strength, along with the location where the measurement was taken.
The user equipment reports are post-processed by a function which continuously monitors the network and estimates the spatial network performance, e.g., coverage and throughput. The UE reporting solution addresses the problems with prior approaches by probing a larger sample of UE locations, reducing the costs involved in drive/walk tests, and continuously tracking the network state as the network and its environment (e.g., topography) evolve.
Post processing of the user equipment reports for network management includes post processing of measured path loss data. Path loss is a term for the attenuation between a source antenna and the RF signal strength at a location within the network. The attenuation is due to antenna characteristics and propagation aspects. Performance in the radio network and path loss resulting from propagation aspects may be separately determined by removing the effect of the antenna characteristics. Such determination is achieved in post processing of the measurement reports.
WO2008/030146 discloses a post-processing technique for calculating path loss to one or more points in a coverage area and mapping the coverage area. The propagation model is based on determination of dominant radiation path to measurement points in the antenna's coverage area. The disclosed technique provides for a joint propagation and antenna model.
C. Brunner and D. Flore, “Generation of Pathloss and Interference Maps as SON Enabler in Deployed UMTS Networks”, IEEE, 69th Vehicular Technology Conference (VTC 2009-Spring), pp. 1-5, 2009. Proposes to generated path loss and interference maps based on signal strength and quality measurements sent in measurement report messages from user equipment to a radio network controller (RNC). The method creates performance maps based on measurement data. A disadvantage with this method is that information about network performance can be provided only for those parts in the network where measurement data is available.
U.S. Pat. No. 7,035,632 disclose another post-processing technique for creating a propagation model for a radio network in order to enable improved radio network management. The propagation model is established based on a priori knowledge of antenna characteristics and an antenna pattern derivable from the antenna characteristics.
However, the true antenna behavior may in many instances differ significantly from what may be established based on a priori knowledge of the antenna characteristics. With deviations between true antenna behavior and an antenna pattern derived from a priori knowledge of antenna characteristics, the resulting propagation model will be misleading and, thus, unsuitable for network management purposes.